From DNA to Protein – Flashcards
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How are the shape and chemical properties of a protein determined
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each protein has a unique sequence of amino acids determines shape and chemical properties
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what are the two manners by which genetic information is expressed
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Transcription and translation
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why is RNA capable of folding in a variety of different shapes
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RNA can fold into a variety of shapes because it is singled stranded
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why is RNA capable of folding in a variety of different shapes
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RNA can fold into a variety of shapes because it is singled stranded
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Name two other ways that RNA differs from DNA
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RNA comes in different varieties structural and catalytic function
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how does transcription begin
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with the opening and unwinding of a small section of DNA
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what is produced by this process
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newly synthesized RNA drops away from the DNA template a double helix is reformed
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how does RNA polymerase function in transcription
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RNA polymerase carry out transcription
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in which direction does the growth occur
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RNA chain grows in 5 to 3
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name four molecules that power this reaction
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ATP, CTP, UTP, GTP
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Why is accuracy not required for transcription
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RNA does not function to permanently store genetic information
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rRNA
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Core of ribosome
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tRNA
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adapters that select amino acids and holds them on the ribosome until incorporated into protein
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miRNA
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regulation of gene expression
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what signals the starting point of transcription on the DNA strand
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RNA polymerase binds to DNA looking for the promoter region
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What terminates transcription
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RNA chain is elongated until polymerase reaches a terminator
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Discuss the sigma factor in bacteria
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Bacteria polymerase has factor that recognizers promoter
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Discuss four manners by which transcription in eukaryotes differs from the process in prokaryotes
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1. Eukaryotes have 3 types of polymerases 2. eukaryotes RNA polymerase requires general transcription factores(accessory proteins) 3. Mechanisms of control less elaborate in eukaryotes (genes are far apart) 4. Eukaryotic DNA is packed into nucleosomes
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What other components are necessary for eukaryotic RNA polymerases to function
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TFIID
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binds to a DNA sequence rich in T and A nucleotides, causes distortion DNA that function to mark the promoter for other transcription factors
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TATA box
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located 25 nucleotides upstream from transcription, binding of other factors hepls form a complete transcription intiation complex
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Capping
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addition of guanine nucleotide with CH3 to 5 end
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polyadenylation
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adenine repeatedly added to 3 end
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where does transcription and processing of RNA occur in eukaryotes
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in the nucleus
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how are exons different from introns
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how are introns removed
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by RNA splicing
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name 2 molecules that play a role in the removal of introns
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nucleotide squences
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what governs the amount of protein produced by an mRNA molecule
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nuclear pore complex
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what is the life span of prokaryotic and eukaryotic mRNAs
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bacterial mRNAs have lifespan of 3 mins, eukaryotic mRNAs have lifespan of 30 mins to 10hrs
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what controls the lifespan of mRNA molecules
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lifespans controlled by nucleotides in 3 untranslated region
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discuss the genetic code
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translation involves conversion of RNA into protein using the genetic code
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charged tRNA
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molecules match amino acids to codons in mRNA
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anticodon
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set of three nucleotides that base pair with the complementary codon
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aminoacyl tRNA synthestases
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covalently joins each amino acid to the proper tRNA molecule
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where within a cell is the RNA message decoded in order to synthesize a protien
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in the ribosomes
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what is a complete ribosome composed of and what is the function of each compoenent
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a large and small subunit
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name the four binding sites on a ribosome
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a-site, aminoacyl-tRNA p-site, peptidyl-tRNA e-site
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discuss the steps involved in translation
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1. charged tRNA molecule enters the a-site 2. the amino acid attached to the newly added tRNA is linked by a peptide bond to the polypeptide chain held by the 3. the large subunit shifts 4. the small subunit moves exactly 3 nucleotides along the mRNA molecule
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define the term ribozyme
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molecule that have catalytic activity
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which codon starts the translation process and which amino acid does it code for
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AUG and tRNA
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what does the term polycistronic indicate
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these mRNA molecules encode different proteins
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name the three codons involved in termination of protein synthesis
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UAA, UAG, UGA
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what happens to the structure of a ribosome once the stop codon is encountered and the mRNA molecule is released
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dissociates into two components
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what are polyribosomes
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large cytoplasmic components made of many ribosomes that are closely spaced along a single strand of mRNA
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discuss on way that inhibitors of protein synthesis can be utilized
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antibiotics
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name two sources of these inhibitors
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no effect on protien synthesis in eukaryotes, can be taken in high doses without being toxic in human
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what is the function of the proteasomes
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act on proteins that have been tagged with ubiqutin
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between DNA and RNA which is more efficient at storing genetic information
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DNA emerged and became more efficient at storing genetic information
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has this always been the case
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the earliest cells are thought to have stored hereditary information in RNA
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Mutagen
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something known to cause mutations (inherited genotypic changes)
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One-gene, One-enzyme Hypothesis (one-gene, one-polypeptide relationship)
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Garrods idea that genes act through the production of enzymes, with each gene responsible for producing a single enzyme that in turn affects a single step in a metabolic pathway
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One-Gene, One-polypeptide relationship
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Many proteins, including many enzymes, are composed of more than one polypeptide chain (or subunit). *The function of a gene is to inform the production of a single, specific polypeptide. (But not all genes code for polypeps.)
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How does information flow from Genes to Proteins?
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-Transcription -Translation The question in another sense is also asking how does Central Dogma take place?
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Transcription
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Information from DNA sequence is copied to form RNA seq. -3 Steps: + Initiation: PROMOTER + Elongation: done by RNA poly. +Termination
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Translation
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RNA seq. is used to create amino acid seq. of a polypeptide
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RNA vs DNA
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-Consists of one polynucleotide strand -Sugar molecue = ribose (rather than deoxyribose in DNA) -"U" uracil instead of "T" (in DNA) -
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Messenger RNA
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- carries a copy of a gene seq. in DNA to the site of protein -Transcript region of one of the strands of DNA -Carries a copy of the gene sequence in the form of codons to the ribosome for protein synthesis.
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Transfer RNA
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A family of double-stranded RNA molecules. Each tRNA carries a specific amino acid and anticodon that will pair with the complementary codon in mRNA during translation.
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Ribosomal RNA
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catalyzes peptide bond formation and provides a structural framework for the ribosome.
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Central Dogma
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Information flows from DNA to RNA to polypeptide. -RNA viruses are exceptions to the central dogma (reverse transcript)
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How is the Information content in DNA transcribed to produce RNA?
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-RNA synthesis is directed by DNA. -Transcription Requires: +DNA template (for complementary base pairing) +Appropriate nucleoside triphosphates (ATP, GTP, CTP, UTP) to act as substrate +* RNA Polymerase enzyme
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RNA Polymerase vs DNA Polymerase
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- RNA does NOT require a primer and it does NOT double check. -Even thought there will be errors in the replication , RNA
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Transcript Step 1: INITIATION
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Done by promoter.
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Promoter
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-tells RNA polymerase where to start transcription and which strand to transcribe. - (special seq. of DNA) is required in order to cataylze RNA polymerase to start working.
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Transcript Step 2: Elongation
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-Once RNA poly. binds to promoter, it unwinds the DNA and reads it from 3-5 direction. -Like DNA polymerase, it adds nucleotides to the 3 ends of the growing strand but doesnt require primer to start working. -
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Consequence of RNA poly not proofreading.
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There will be a lot of mutations/ errors. -However, many correct copies of RNA are made at the same time and because RNA has a short life span, these errors are not as harmful as mutations to DNA.
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Mutations in DNA vs Mutations in RNA
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-It is deleterious (usually) to have mutated DNA because DNA is the main set of genes that will be replicated and not many are replicated (in comparison to RNA). On the other hand,many RNA are created and RNAs life span is short so a mutation is not really that harmful
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Transcription and Translation Occurence
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Pro: At the same time in the cytoplasm Euk: Transcribe in Nucleus and translate in Cytoplasm
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Gene Structure
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Pro: DNA seq. is read in the same order as the amino acid seq. Euk: Noncoding introns within coding seq.
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Modification of mRNA after initial transcription but before translation
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Pro: None Euk: Introns spliced out; 5 cap and 3 poly A added
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pre-mRNA
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-primary mRNA transcript where introns and exons are. -still processing in the nuclues -mRNA is the mature product that leaves the nuclues and goes into cytoplasm to be translated
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introns
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noncoding base sequences. (intervening regions) -introns are removed before the pre-mRNA becomes mature mRNA.
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exons
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(expressed regions) introns may be interspersed with coding seq. (only exons are left to create mRNA)
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exons
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(expressed regions) introns may be interspersed with coding seq. (only exons are left to create mRNA)
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exons
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(expressed regions) introns may be interspersed with coding seq. (only exons are left to create mRNA)
